doc: fix the example for embedders

Refs: nodejs#42670

PR-URL: nodejs#42671
Fixes: nodejs#42670
Reviewed-By: Darshan Sen <raisinten@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Mestery <mestery@protonmail.com>
Reviewed-By: Akhil Marsonya <akhil.marsonya27@gmail.com>

Author: mmomtchev

doc/api/embedding.md

@@ -124,6 +124,7 @@ int RunNodeInstance(MultiIsolatePlatform* platform,
   {
     Locker locker(isolate);
     Isolate::Scope isolate_scope(isolate);
+    HandleScope handle_scope(isolate);
     // The v8::Context needs to be entered when node::CreateEnvironment() and
     // node::LoadEnvironment() are being called.
     Context::Scope context_scope(setup->context());